Oct. 7, 2011 -- Men should just say "no" to prostate cancer screening with the common PSA blood test, according to draft guidelines from the U.S. Preventive Services Task Force.

About a third of men over age 40, and about half of men age 65 to 79, get regular blood tests for prostate specific antigen, or PSA.

Rising PSA levels are an early sign of prostate cancer, but the test gives a false cancer signal up to 80% of the time. Moreover, not all PSA-detected prostate cancers are dangerous.

"The common perception that PSA-based early detection of prostate cancer saves lives is simply not supported by the scientific evidence," task force co-vice chair Michael L. LeFevre, MD, MSPH, professor of family and community medicine at the University of Missouri, tells WebMD.

The task force's draft statement, leaked to the press a week early, will be open for public comment next week before becoming the official recommendation of the U.S. government's top expert guideline panel.

The statement already is drawing harsh criticism, particularly from the American Urological Association.

"It is our feeling that, when interpreted appropriately, the PSA test provides important information," AUA President Sushil S. Lacy, MD, says in a news release. "Until there is a better widespread test for this potentially devastating disease, the [task force] -- by disparaging the test -- is doing a great disservice to the men worldwide who may benefit from the PSA test."

Criticism also comes from biostatistics expert Ruth Etzioni, PhD, of the Fred Hutchinson Research Center. Etzioni has served on prostate-cancer screening guidelines panels of the AUA, the American Cancer Society, and the National Comprehensive Cancer Network.

"The task force is oversimplifying a complex series of [clinical trial] results," Etzioni tells WebMD. "I think there is real evidence of benefit for PSA screening. Death rates from prostate cancer have gone down … It is hard for me to believe all that is due to better treatment. "But Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society, says the proposed guidelines reflect the hard reality that PSA testing does not appear to save lives.

"In the American Cancer Society's 2010 guidelines, we said we were uncertain: The evidence is not convincing that PSA testing works," Lichtenfeld tells WebMD. "We feel the task force came to a reasonable conclusion."

Just as women once were told that hormone replacement therapy would prevent heart disease -- until scientific studies showed that it did not -- Lichtenfeld says current evidence strongly suggests that doctors were wrong to tell men that PSA testing would protect them from dying from prostate cancer.

"Men need to know the truth," Lichtenfeld says. "We have gone through 20 years where we have had strong voices telling us PSA testing works. So there is a huge component of men who believe PSA testing has saved their lives. Now, when we say it wasn't necessarily so, that becomes a difficult conversation."

PSA: Harm Without Benefit?

The idea of PSA screening is that it will detect early prostate cancers that can be cured. But clinical trials fail to show that PSA screening cuts prostate-cancer death rates.

"At this point we have had over 370,000 men enrolled in clinical trials, and we still do not see a significant benefit," LeFevre says. "If there is a benefit, it is very small. That is different from zero benefit, but the true benefit is somewhere between small and none."

The harm from a PSA test is that a positive test leads to a biopsy. Biopsy can detect prostate cancer -- but that's where troubles begin.

"The major problem is that most of the cancers we detect do not need to be treated, but we do not know which ones do need to be treated," LeFevre says. "And these treatments do have significant harms."

Etzioni argues that the Gleason score -- a scale used to evaluate prostate cancer severity -- tells doctors which cancers should be treated and which should not. But Lichtenfeld agrees with LeFevre that "we do not have a test to tell which cancers are indolent and which are aggressive."

Once they learn they have a prostate cancer, most U.S. men want treatment. And LeFevre notes that treatment carries very real risks.

For every 1,000 men who undergo prostate-cancer surgery, five die within a month. Another 10 to 70 men will have complications of surgery. And 200 to 300 of these men will go on to have long-term urinary incontinence, impotence, or both.

"The net result is that doctors and patients and families are going to have to have very careful conversations with their doctors that really emphasize what the scientific evidence shows," Lichtenfeld says. "And that is not overwhelmingly in favor of PSA testing."

Even though Etzioni supports PSA testing, she says only a certain group of men should seek it.

"I really think a man should go in for a PSA test if he is going to be comfortable with the notion of living with a low-risk cancer," she says. "The problem is that we as a society are not able to hear the word 'cancer' and not want to treat it. We need to understand prostate cancer better and know it is a very variable disease. There are high-risk cases that need to be treated and many, many low-risk cases that do not."